Victoria Geenes

Lysophosphatidic Acid Is a Potential Mediator of Cholestatic Pruritus

BACKGROUND & AIMS Pruritus is a common and disabling symptom in cholestatic disorders. However, its causes remain unknown. We hypothesized that potential pruritogens accumulate in the circulation of cholestatic patients and activate sensory neurons. METHODS Cytosolic free calcium ([Ca(2+)](i)) was measured in neuronal cell lines by ratiometric fluorometry upon exposure to serum samples from pruritic patients with intrahepatic cholestasis of pregnancy (ICP), primary biliary cirrhosis (PBC), other cholestatic disorders, and pregnant, healthy, and nonpruritic disease controls. Putative [Ca(2+)](i)-inducing factors in pruritic serum were explored by analytical techniques, including quantification by high-performance liquid chromatography/mass spectroscopy. In mice, scratch activity after intradermal pruritogen injection was quantified using a magnetic device. RESULTS Transient increases in neuronal [Ca(2+)](i) induced by pruritic PBC and ICP sera were higher than corresponding controls. Lysophosphatidic acid (LPA) could be identified as a major [Ca(2+)](i) agonist in pruritic sera, and LPA concentrations were increased in cholestatic patients with pruritus. LPA injected intradermally into mice induced scratch responses. Autotaxin, the serum enzyme converting lysophosphatidylcholine into LPA, was markedly increased in patients with ICP versus pregnant controls (P < .0001) and cholestatic patients with versus without pruritus (P < .0001). Autotaxin activity correlated with intensity of pruritus (P < .0001), which was not the case for serum bile salts, histamine, tryptase, substance P, or mu-opioids. In patients with PBC who underwent temporary nasobiliary drainage, both itch intensity and autotaxin activity markedly decreased during drainage and returned to preexistent levels after drain removal. CONCLUSIONS We suggest that LPA and autotaxin play a critical role in cholestatic pruritus and may serve as potential targets for future therapeutic interventions.

Association of severe intrahepatic cholestasis of pregnancy with adverse pregnancy outcomes: A prospective population-based case-control study

Intrahepatic cholestasis of pregnancy (ICP) is a pregnancy‐specific liver disease, characterized by maternal pruritus and raised serum bile acids. Our objectives were to describe the epidemiology and pregnancy complications associated with severe ICP and to test the hypothesis that adverse perinatal outcomes are increased in these women. A prospective population‐based case‐control study with national coverage was undertaken using the UK Obstetric Surveillance System (UKOSS). Control data for comparison were obtained from women with healthy pregnancy outcome through UKOSS (n = 2,232), St Marys Maternity Information System (n = 554,319), and Office for National Statistics (n = 668,195). The main outcome measures investigated were preterm delivery, stillbirth, and neonatal unit admission. In all, 713 confirmed cases of severe ICP were identified, giving an estimated incidence of 9.2 per 10,000 maternities. Women with severe ICP and a singleton pregnancy (n = 669) had increased risks of preterm delivery (164/664; 25% versus 144/2200; 6.5%; adjusted odds ratio [OR] 5.39, 95% confidence interval [CI] 4.17 to 6.98), neonatal unit admission (80/654; 12% versus 123/2192; 5.6%; adjusted OR 2.68, 95% CI 1.97 to 3.65), and stillbirth (10/664; 1.5% versus 11/2205; 0.5%; adjusted OR 2.58, 95% CI 1.03 to 6.49) compared to controls. Seven of 10 stillbirths in ICP cases were associated with coexisting pregnancy complications. These differences remained significant against national data. Risks of preterm delivery, meconium‐stained amniotic fluid, and stillbirth rose with increasing maternal serum bile acid concentrations. Conclusion: In the largest prospective cohort study in severe ICP to date, we demonstrate significant increased risks of adverse perinatal outcomes, including stillbirth. Our findings support the case for close antenatal monitoring of pregnancies affected by severe ICP. (Hepatology 2014;59:1482‐1491)

A comprehensive analysis of common genetic variation around six candidate loci for intrahepatic cholestasis of pregnancy.

OBJECTIVES:Intrahepatic cholestasis of pregnancy (ICP) has a complex etiology with a significant genetic component. Heterozygous mutations of canalicular transporters occur in a subset of ICP cases and a population susceptibility allele (p.444A) has been identified in ABCB11. We sought to expand our knowledge of the detailed genetic contribution to ICP by investigation of common variation around candidate loci with biological plausibility for a role in ICP (ABCB4, ABCB11, ABCC2, ATP8B1, NR1H4, and FGF19).METHODS:ICP patients (n=563) of white western European origin and controls (n=642) were analyzed in a case–control design. Single-nucleotide polymorphism (SNP) markers (n=83) were selected from the HapMap data set (Tagger, Haploview 4.1 (build 22)). Genotyping was performed by allelic discrimination assay on a robotic platform. Following quality control, SNP data were analyzed by Armitages trend test.RESULTS:Cochran–Armitage trend testing identified six SNPs in ABCB11 together with six SNPs in ABCB4 that showed significant evidence of association. The minimum Bonferroni corrected P value for trend testing ABCB11 was 5.81×10−4 (rs3815676) and for ABCB4 it was 4.6×10−7(rs2109505). Conditional analysis of the two clusters of association signals suggested a single signal in ABCB4 but evidence for two independent signals in ABCB11. To confirm these findings, a second study was performed in a further 227 cases, which confirmed and strengthened the original findings.CONCLUSIONS:Our analysis of a large cohort of ICP cases has identified a key role for common variation around the ABCB4 and ABCB11 loci, identified the core associations, and expanded our knowledge of ICP susceptibility.

Intrahepatic cholestasis of pregnancy

Obstetric cholestasis is also known as intrahepatic cholestasis of pregnancy (ICP). ICP affects approximately 0.7% of pregnant women in the UK, equating to approximately 6000 women per year. Pruritus, elevated liver enzymes and raised serum bile acids are key to the diagnosis of ICP. There is an increased risk of adverse perinatal outcomes associated with severe ICP, including spontaneous preterm birth, meconium staining of the amniotic fluid and stillbirth. ICP may be treated with ursodeoxycholic acid (UDCA), with some improvement in serum biochemistry and pruritus; however, the impact on the fetus is uncertain.

A placental phenotype for intrahepatic cholestasis of pregnancy

Intrahepatic cholestasis of pregnancy (ICP) is a pregnancy specific liver disease associated with significant risk of fetal complications. It is hypothesised that the risk of adverse fetal outcomes relates to the toxic effects of bile acids, the levels of which are increased in both maternal and fetal serum. Human and rodent studies have shown that transplacental transfer of bile acids is impaired in ICP. Furthermore, the morphology of placentas from the rodent model of ICP is markedly abnormal, and is associated with increased expression of apoptotic markers and oxidative stress. Using placental tissue from ICP cases and normal pregnancies and cultured placental explant fragments we investigated the histological and molecular effects of cholestasis. We also examined the influence of ursodeoxycholic acid (UDCA) administration on these parameters. Here we report that ICP is associated with several morphological abnormalities of the placenta, including an increase in the number of syncytial knots, and that these can be reproduced in an in vitro (explant) model exposed to the bile acids taurocholic acid and taurochenodoexycholic acid. Furthermore, we demonstrate that ursodeoxycholic acid, a drug commonly used in the management of ICP, has a protective effect on placental tissue both in vivo and in vitro.

Autotaxin activity has a high accuracy to diagnose intrahepatic cholestasis of pregnancy

BACKGROUND & AIMS Intrahepatic cholestasis of pregnancy (ICP) is defined by pruritus, elevated total fasting serum bile salts (TBS) and transaminases, and an increased risk of adverse fetal outcome. An accurate diagnostic marker is needed. Increased serum autotaxin correlates with cholestasis-associated pruritus. We aimed at unraveling the diagnostic accuracy of autotaxin in ICP. METHODS Serum samples and placental tissue were collected from 44 women with uncomplicated pregnancies and 105 with pruritus and/or elevated serum transaminases. Autotaxin serum levels were quantified enzymatically and by Western blotting, autotaxin gene expression by quantitative PCR. RESULTS Serum autotaxin was increased in ICP (mean ± SD: 43.5 ± 18.2 nmol ml(-1)min(-1), n=55, p<0.0001) compared to other pruritic disorders of pregnancy (16.8 ± 6.7 nmol ml(-1)min(-1), n=33), pre-eclampsia complicated by HELLP-syndrome (16.8 ± 8.9 nmol ml(-1)min(-1), n=17), and pregnant controls (19.6 ± 5.7 nmol ml(-1)min(-1), n=44). Longitudinal analysis during pregnancy revealed a marked rise in serum autotaxin with onset of ICP-related pruritus. Serum autotaxin was increased in women taking oral contraceptives. Increased serum autotaxin during ICP was not associated with increased autotaxin mRNA in placenta. With a cut-off value of 27.0 nmol ml(-1)min(-1), autotaxin had an excellent sensitivity and specificity in distinguishing ICP from other pruritic disorders or pre-eclampsia/HELLP-syndrome. Serum autotaxin displayed no circadian rhythm and was not influenced by food intake. CONCLUSIONS Increased serum autotaxin activity represents a highly sensitive, specific and robust diagnostic marker of ICP, distinguishing ICP from other pruritic disorders of pregnancy and pregnancy-related liver diseases. Pregnancy and oral contraception increase serum autotaxin to a much lesser extent than ICP.

The Reversed Feto-Maternal Bile Acid Gradient in Intrahepatic Cholestasis of Pregnancy Is Corrected by Ursodeoxycholic Acid

Intrahepatic cholestasis of pregnancy (ICP) is a pregnancy-specific liver disorder associated with an increased risk of adverse fetal outcomes. It is characterised by raised maternal serum bile acids, which are believed to cause the adverse outcomes. ICP is commonly treated with ursodeoxycholic acid (UDCA). This study aimed to determine the fetal and maternal bile acid profiles in normal and ICP pregnancies, and to examine the effect of UDCA treatment. Matched maternal and umbilical cord serum samples were collected from untreated ICP (n = 18), UDCA-treated ICP (n = 46) and uncomplicated pregnancy (n = 15) cases at the time of delivery. Nineteen individual bile acids were measured using HPLC-MS/MS. Maternal and fetal serum bile acids are significantly raised in ICP compared with normal pregnancy (p = <0.0001 and <0.05, respectively), predominantly due to increased levels of conjugated cholic and chenodeoxycholic acid. There are no differences between the umbilical cord artery and cord vein levels of the major bile acid species. The feto-maternal gradient of bile acids is reversed in ICP. Treatment with UDCA significantly reduces serum bile acids in the maternal compartment (p = <0.0001), thereby reducing the feto-maternal transplacental gradient. UDCA-treatment does not cause a clinically important increase in lithocholic acid (LCA) concentrations. ICP is associated with significant quantitative and qualitative changes in the maternal and fetal bile acid pools. Treatment with UDCA reduces the level of bile acids in both compartments and reverses the qualitative changes. We have not found evidence to support the suggestion that UDCA treatment increases fetal LCA concentrations to deleterious levels.

Rifampicin in the treatment of severe intrahepatic cholestasis of pregnancy.

OBJECTIVE To describe the use of combined ursodeoxycholic acid (UDCA) and rifampicin treatment in intrahepatic cholestasis of pregnancy (ICP). STUDY DESIGN A questionnaire survey of 27 women with 28 affected pregnancies identified via the UK and International Obstetric Medicine forum. The clinical case notes of women with ICP treated with combined UDCA and rifampicin therapy were reviewed, and data regarding maternal and perinatal outcomes extracted. RESULTS Serum bile acids remained high whilst taking UDCA as monotherapy. In 14 pregnancies (54%) serum bile acids decreased following the introduction of rifampicin. In 10 pregnancies (38%), there was a 50% reduction in serum bile acids. There were no adverse effects reported with either drug. CONCLUSIONS This is the first report of the use of rifampicin in ICP. The data suggest that combined treatment with UDCA and rifampicin is an effective way of treating women with severe ICP who do not respond to treatment with UDCA alone.

Bile Acid Signaling in Fetal Tissues: Implications for Intrahepatic Cholestasis of Pregnancy

Background/Aims: Intrahepatic cholestasis of pregnancy (ICP) is complicated by spontaneous preterm labor, fetal anoxia and unexplained fetal death. We aim to evaluate the mechanisms by which raised fetal bile acids cause placental abnormalities and fetal cardiac pathology. Methods: The study was performed using placental samples taken from ICP pregnancies, placental explant culture, neonatal and adult cardiomyocytes, and murine and human embryonic stem cell-derived cardiomyocytes. Results: Maternal cholestasis causes a placental phenotype with histological abnormalities. This can be evaluated using placental explant cultures. Taurocholate, the principal bile acid raised in the fetal compartment in ICP, causes abnormal cardiomyocyte contraction, rhythm and desynchronization of calcium dynamics. To extend our observations that the muscarinic M2 receptor plays a role in bile acid-induced arrhythmia in cardiomyocytes, we are developing a model containing mixed cell populations to represent the fetal and maternal hearts. This will be used to evaluate the underlying mechanisms to explain fetal arrhythmia in the presence of cholestasis. Conclusion: Bile acids signal via a spectrum of pathways in the placenta and the fetal heart.

Effect of maternal cholestasis on TGR5 expression in human and rat placenta at term

BACKGROUND & AIMS TGR5 (Gpbar-1) is a plasma membrane-bound bile acid receptor expressed in several tissues, including liver, intestine and brain. High levels of TGR5 mRNA have been detected in human and rodent placenta, however, localization of the TGR5 protein has not been studied in this tissue. We aimed at characterizing TGR5 expression in placental tissue and investigated the effect of bile acids and progesterone metabolites, which accumulate during intrahepatic cholestasis of pregnancy (ICP), on receptor expression and localization. METHODS TGR5 mRNA levels and cell-specific localization were determined by quantitative PCR and immunofluorescence, respectively. RESULTS In human term placentas, TGR5 was mainly localized in fetal macrophages and to a lower extent in trophoblasts. In placentas from ICP patients and pregnant rats with obstructive cholestasis a marked down-regulation of TGR5 mRNA expression was observed. However, the cell-specific distribution of the TGR5 protein was unaffected. Besides bile acids, progesterone and its metabolites (5α-pregnan-3α-ol-20-one/5α-pregnan-3β-ol-20-one), which increase in serum during ICP, were able to dose-dependently activate TGR5. In addition, progesterone metabolites but not their sulfated derivatives nor taurolithocholic acid, significantly down-regulated TGR5 mRNA and protein expression in isolated human macrophages and a macrophage-derived cell line. CONCLUSION Since fetal macrophages and trophoblast cells are exposed to changes in the flux of compounds across the placental barrier, the expression of TGR5 in these cells together with its sensitivity to bile acids and progesterone metabolites regarding receptor activity and mRNA expression suggest that TGR5 may play a role in the effect of maternal cholestasis on the placenta.